Sex determination is decided by the 23rd pair of chromosomes commonly known as the sex chromosomes. Males have XY as their 23rd pair and females have XX. A female gamete, the ovum, can only receive only the X chromosome and the male gamete, the spermatozoon can receive either the X or the Y chromosome when meiosis occurs. Therefore the male sperm is responsible for the sex determination of the baby. Example: Figure 1: a Punnet square showing that there is an equal opportunity for a foetus to develop into either a male or female. It also shows how the male gamete determines the foetus sex by combining the X chromosome with either an X or Y chromosome. Once the sperm fuses with the ovum both chromosomes will pair up and begin the first stages of cell division. It won't be until the 6th week of gestation that we can start to determine the foetus' sex. This is because the testes determining factor (TDF), a hypothetical substance that does as its name says it does. It will determine whether the foetus develops testes or not. The reason it isn't called ovaries determining factor is because the Y chromosome controls the development of the testes. On the Y chromosome there is a region called sex-determining region of the Y, SRY, this is the region that has the genes to control the growth of the testes. If the Y chromosome is not present then there is no SRY therefore the male gonadal tissue (see later) will not develop and the female gonadal tissue will take advantage and develop into the female reproductive system. Development of the Male Internal Reproductive System Once the SRY gene is activated, it will cause the secretion of Mullerian-inhibiting substance (MIS) by the Sertoli cells within the seventh ... ... middle of paper ... ...e distal ends of the Mullerian ducts will form the oviducts, uterus and vagina. The opposite ends will form the fallopian tubes. The genital tubercle will from the clitoris, urethral folds remain open as the labia minora and the labioscrotal swellings become the labia majora. Summary The SRY gene is the initiator of sex determination and unless this gene is present all developing foetuses will be female. This is due to the high level of female hormones in the blood from the mother. It isn't until the Y chromosome is present with the SRY gene on it to degenerate the female tracts (Mullerian) and promote male tracts (Wolffian) by the release of anti-Mullerian substance and the stimulation of the Sertoli cells to secrete testosterone which leads to the release of hCG to stimulate the release of DHT to promote growth further and overcome the maternal hormones.
The predominant theory for the origin of sex has always been the benefits of DNA repair. In an asexual haploid cell, if both sides of a DNA strand were damaged—for instance, if the thymine and adenine erred and became unrecognizable—since the cell would have only one copy of the information, there would be no chance for the cell to repair the damage and the cell would either die or be able to pass on only grossly mutated genes. However, an asexual diploid cell and a sexual cell each contain an extra set of chromosomes providing the template to repair that damaged DNA strand. Using DNA r...
The first category of Dr. Bushong's theory is genetics. Due to defects in fertilization, fetuses can have a chromosomal pattern of XXXY (mosaic hermaphrodite), XXY, or XYY. These abnormalities result in deformed genitalia, sterility, or an individual whose physical appearance as one sex does not match their genetic makeup as a member of the other...
This means that all the sperm in males and eggs in females are produced from meiosis. Sperm and egg cells are haploid cells-they contain only one of each type of chromosome. Meiosis actually starts with a diploid cell that undergoes two divisions; the end products are four gametes, all genetically different. Meiosis is known as a reduction division because the daughter cells always contain half the amount of chromosomes as the diploid beginner cell. Chromosomes come in pairs and these pairs are called homologous pairs. Homologous chromosomes mean that both of the chromosomes in the pair have the same gene sequence. Human somatic cells(diploid) contain 46 chromosomes consisting of 23 homologous pairs; therefore, human gametes, which are haploid, have 23 total chromosomes-one from each homologous pair. Just like in mitosis, meiosis undergoes all of the same phases. However, because meiosis involves two divisions, the cell goes through all the phases twice. When referring to the first time the cell undergoes a phase, we say 1, and when referring to the second time, we say 2. For example, when a cell starts prophase the first time in meiosis, we say it is going through prophase 1(P1). Also, there are some differences in the process itself. During P1, homologous chromosomes exchange a section of themselves in what is known as crossing over. This provides a source of genetic variation since part of each chromosome switched places with each other, thus making both chromosomes distinct from the original. Another important difference to know is that in anaphase 1, the doubled chromosomes are not separated into sister chromatids. This doesn’t happen until A2 to ensure that each of the four gametes receives one of each kind of chromosome. There are many key points to understand about meiosis. The first being that cells in meiosis do not go through interphase twice. Interphase is a “one-time” thing; DNA
Gender selection through prenatal diagnosis and abortion has existed since the 1970s. More recently, pre-implantation sexing of embryos for transfer has been developed. Both prenatal and pre-implantation methods of gender selection are seen as horrible unethical and impractical because they require abortion or a costly, intrusive cycle of in vitro fertilization and embryo discard (Hill et al. 438). Through this process if an embryo turns out to be...
A male makes one thousand new sperm per second, that is two trillion over a lifetime and they all are one of a kind, very unique. A woman has all her eggs from birth. The process starts out as meiosis, this is where 30,000 genes are then there are forty six chromosomes. Twenty three comes from your mother and twenty three come from your father, they only come together in meiosis in pairs, but they are not the same. Chromosomes make an exact copy of themselves then they condense making an X shape, chromosomes get a partner then embrace. The chromosomes cling close together in big chunks, the cell then divides pulling the pair apart with twenty three chromosomes. The cell alone is incomplete, but holds many promises. Every cell holds di...
To begin with, gender must be examined at the basic level of science in regard to physical and biological development of humans. We all understand the physical differences between the male and female gender, but how is our sex actually determined. After conception,
Most children become aware of their anatomic sex by the age of eighteen months and by three years old the child has a sense of gender identity (Rathus, Nevid, & Fichner-Rathus, 2014, p. 159). Gender identity is most consistent with chromosomal sex. There is intersexual whom possesses the gonads of one anatomic sex but external gentilia that are ambiguous or like the other anatomic sex. This is when nature and nurture comes in nature refers to the biology and nurture refers to the environmental influences. Lastly hermaphrodites are pretty rare, a hermaphrodite is a person whom has both ovarian and testicular
... the sperm must become semen. To accomplish this, glands in the vas deferens, such as the prostate, bulbourethral, and the seminal glands will be secreted in order to sustain and foster the gamete. All together, semen is made, which is a milky, white male reproductive fluid. As coitus is occurring, a male will become sexually aroused and ejaculate, which moves the semen to the urethra and from there it will be inserted into the vagina and then to the fallopian tube to become fertilized.
Occasionally, an “error” so to speak occurs during the meeting of the autosomes and chromosomes. When this happens, many deformities can occur within the developing fetus, one such outcome is ambiguous biological sex, or, intersexed. This essentially means a person that has either external sex organs of both a m...
Gender is determined by the sex chromosomes, XX produces a female, and XY produces a male. Males are produced by the action of the SRY gene on the Y chromosome, which contains the code necessary to cause the indifferent gonads to develop as testes (1). In turn the testes secrete two kinds of hormones, the anti-Mullerian hormone and testosterone, which instruct the body to develop in a masculine fashion (1). The presence of androgens during the development of the embryo results in a male while their absence results by default in a female. Hence the dictum "Nature's impulse is to create a female" (1). The genetic sex (whether the individual is XX or XY) determines the gonadal sex (whether there are ovaries or testis), which through hormonal secretions determines the phenotypic sex. Sexual differentiation is not drive...
Inside the cells that produce sperm and eggs, chromosomes become paired. While they are pressed together, the chromosomes may break, and each may swap a portion of its genetic material for the matching portion from its mate. This form of recombination is called crossing-over. When the chromosomes glue themselves back together and separate, each has picked up new genetic material from the other. The constellation of physical characteristics it determines is now different than before crossing-over.
Over the past five decades, surgical interventions have been recommended as standard procedure for infants who are born with either ambiguous genitalia or who suffer from traumatic genital injury. Surgical advances in this century have made it possible for physicians to choose a gender for the child and then sculpt the appropriate genitalia. Some of the conditions that demand gender reassignment for children can be a result of chromosomal or hormonal defects.
Although this is mostly correct, there are some variations to the rule in which a person will differ from the assigned chromosomes and have physiological differences that will affect gender identity development. Eliza Dragowski, an assistant professor of psychology, writes in a report titled Childhood Gender Identity. Disorder? Developmental, Cultural, and Diagnostic Concerns, "The second path points to anatomical brain differences.
We all know that women have two “X” chromosomes and men have one “X” and one “Y” chromosome. The X and Y chromosomes determine a person’s sex. Chromosomes contain the set of instructions to create living being. The male Y chromosome and female X chromosome are different in size and vary in the number of working genes. The X chromosome can contain more than 1,000 working genes, while the Y has less than 100.
Sex Selection is usually thought of as a procedure that occurs prior to conception, however, that is not always the case. Sex selection is a method that is used prior to and after conception. Focusing on after conception and birth, sex selection can take place by genetically testing, or by taking ultrasound images of the developing fetus, resulting in abortion due to an undesired gender. The practice of sex selection can also take place after birth of the child, “[…] when one or both parents kill their baby” (Dixon).